For example, in a photolithography process of a semiconductor device manufacturing process, a predetermined resist pattern is formed on a wafer by sequentially performing, for example, a resist coating process of coating a resist liquid on a semiconductor wafer (hereinafter referred to as a “wafer”) as a substrate to form a resist film, an exposure process of exposing a predetermined pattern in the resist film, a heating process (post-exposure baking process) of promoting a chemical reaction within the resist film after the exposure, a developing process of developing the exposed resist film, and so forth.
As developing methods, there are known a method of, while supplying a developing solution from a long nozzle having a length substantially equal to a diameter of a wafer, parallel-moving the nozzle from one end portion of the wafer toward the other end portion thereof, and a method of supplying a developing solution onto a wafer rotating at a high speed and diffusing the developing solution.
However, when the developing process is performed by the long nozzle, a difference in the developing solution contact time is generated in one end portion and the other end portion of the wafer. Furthermore, even when the developing solution is supplied to the center of the rotating wafer, a difference in the developing solution contact time is generated in the central portion of the wafer and the outer peripheral portion thereof. As a result, a variation in the line width of the resist pattern subjected to the developing process is generated within a wafer plane. Along with the recent miniaturization of a resist pattern attributable to the high integration of a semiconductor device, the variation in the line width caused by the difference in the developing time has become impermissible.
Thus, in order to uniformly perform a developing process within a wafer plane, study has been made on a method of using a developing solution supply nozzle (hereinafter often referred to as a “PAD nozzle”) having a liquid contact surface, for example, parallel to a substrate. Specifically, a developing solution is first supplied onto a substrate, which is not rotating, while securing a gap of a predetermined size between the liquid contact surface of the developing solution supply nozzle and the wafer, thereby forming a liquid film of the developing solution between the developing solution supply nozzle and the wafer. At this time, the developing solution supply nozzle is positioned in the central portion of the substrate. Then, the wafer is rotated at a low speed of about 30 rpm. While continuing to supply the developing solution from the developing solution supply nozzle, namely while maintaining the liquid film of the developing solution between the developing solution supply nozzle 300 and the substrate, the developing solution supply nozzle 300 is moved to the outer peripheral portion of the wafer W as illustrated in FIG. 25. This makes it possible to supply the developing solution Q onto the entire surface of the wafer W and to realize a uniform developing process within a wafer plane.
From the viewpoint of improving the throughput of wafer processing, it is preferred that the developing time is as short as possible. However, according to the study conducted by the present inventors, it was confirmed that if the developing time is made short in a developing process which makes use of a PAD nozzle, the points at which the line width of a resist pattern does not become a desired value are spirally generated within a wafer plane, for example, as illustrated in FIG. 26. In FIG. 26, the line width of a resist pattern within a wafer plane is measured at multiple points on a shot-by-shot basis and the degree of variation in the line width in each shot is illustrated by color shading. In addition, FIG. 26 illustrates a case where the developing time is, for example, 30 seconds. However, it was confirmed that, if the developing time is 60 seconds, as illustrated in FIG. 27, the tendency to become spiral is scarcely seen and the line width within the wafer plane is substantially uniform.